The present invention relates to an arrangement for the relative angular position change of two drivingly connected shafts, especially between a crankshaft supported in an engine housing of an internal combustion engine and a cam shaft which includes an adjusting mechanism and an actuating mechanism as disclosed in the U.S. Pat. No. 3,258,937.
In this prior art arrangement, the driving gear is non-rotatably connected with a unilaterally axially extended hub, whereby the hub is rotatably supported near the driving gear in an engine housing. At its free end, it is rotatably supported by way of a cylindrical collar in an end-face aperture of a cam shaft for a fuel injection pump. The cam shaft is rotatably supported also in the engine housing near the coupling area with the hub. The cam shaft and the hub are provided with apertures, starting from the end faces on the coupling side, that include form-locking guidances for the coupling member. The coupling member which is axially adjustable relative to the driving gear, respectively, its hub for the angular position change, is acted upon on one side hydraulically for the adjustment and is supported on the other side by way of a return spring in the direction of the starting position. The hydraulic medium which is to be supplied for effecting an angular position change and for maintaining a predetermined angular position change, is supplied by way of channels within the area of the bearing of the hub to a control space which is axially limited on one side by an end face of the coupling member.
With the use of a return spring for the coupling member, only relatively low adjusting velocities can be attained. The magnitude of the prestress and the spring constant of the return spring are limited in their value because with increasing adjusting travel an equilibrium force has to be opposed on the hydraulic side to the spring force resulting therefrom. In the hydraulic medium which on its path from the pump driven by the internal combustion engine to the control space limited on one side by the coupling member, is conducted over a bearing gap of the slide bearing of the hub in the engine housing, an increased pressure has to be supplied by the pump with an increasing spring force which leads to an increasing medium loss through the slide bearing gap. A completely satisfactory angular position change of the cam shaft relative to its driving gear is thus no longer assured over the entire operating range of the internal combustion engine. Additionally, a curve of the pressure level in the control chamber to the coupling member will result from this sealing problem over the rotational speed range of the internal combustion engine which is not suited for a continuous Proportional adjustment of the coupling member. Of further disadvantage are the adjusting velocities of the coupling member differing in the two directions with the use of a return spring.
An arrangement for the relative angular position change of a cam shaft to the crankshaft of an internal combustion engine is disclosed in the EP-OS No. 163,046, in which an active hydraulic adjustment in opposite directions is possible. However, this arrangement, like the aforementioned arrangement according to the U.S. Pat. No. 3,258,937, discloses hydraulically adjustable elements arranged in rotating parts of the arrangement, connected with the problem of the feed of the hydraulic medium from fixed parts of the internal combustion engine into the rotating parts, respectively, arrangements of the mechanism for the relative angular position change.
This problem of the seal influences, inter alia, also the arrangement of such a mechanism for the relative angular position change in the engine housing of an internal combustion engine. With the aforementioned mechanisms, the leakage oil leaving through bearing gaps is fed within the engine housing to the respective collecting space. The pressure loss connected with the leakages out of the bearing gaps is thereby accepted.
However, such leakages, respectively pressure losses cannot be accepted or tolerated for a fine control of a hydraulically actuated mechanism for the relative angular position change. A mechanism, in which non-controllable leakages are avoided is disclosed in the U.S. Pat. No. 2,191,459. This mechanism, similar to the aforementioned mechanism according to the U.S. Pat. No. 3,258,937, discloses a coupling member form-lockingly connected, on the one hand, with the cam shaft and, on the other hand, with the hub of a driving gear whereby the coupling member is axially adjusted in one direction by a return spring and in the opposite direction hydraulically. In order to be able to permit in this mechanism to the pressure produced by a pump driven by the crankshaft to act on the piston of the coupling member without significant pressure loss owing to leakages, the rotating hub of the driving gear which is open end-face for the admission of the hydraulic medium to the piston, is sealed with respect to a coaxial bore in a housing wall. This arrangement is so made that in case of a leakage as a result of the defective seal, the hydraulic medium in the engine housing is conducted to the collecting space.